Effects of (+)-Catechin on the Composition, Phenolic Content and Antioxidant Activity of Full-Fat Cheese during Ripening and Recovery of (+)-Catechin after Simulated In Vitro Digestion

Abstract

(+)-Catechin, the representative catechin in green tea, was incorporated into a full-fat cheese (at 125-500 ppm) followed by ripening for 90 days at 8 °C and digesting for six hours. Determination of pH, proximate composition, total phenolic content (TPC) and antioxidant activity (AA) after manufacture and ripening demonstrated that the addition of (+)-catechin significantly (p ≤ 0.05) decreased the pH of both whey and curd during cheese manufacturing and ripening with no significant (p > 0.05) effect on the moisture, protein and fat contents. (+)-Catechin increased TPC, as well as AA, though the increase was not proportional with increasing the concentration of added (+)-catechin. About 57%-69% of (+)-catechin was retained in the cheese curd, whereas about 19%-39% (depending on the concentration) was recovered from the cheese digesta. Transmission electron micrographs showed that the ripened control cheese had a homogeneous pattern of milk fat globules with regular spacing entrapped in a homogenous structure of casein proteins, whereas the addition of (+)-catechin disrupted this homogenous structure. The apparent interaction between (+)-catechin and cheese fat globules was confirmed by Fourier transform infrared spectroscopy. These associations should be taken into account when incorporating antioxidants, such as (+)-catechin, to create functional dairy products, such as cheese.

Keywords: cheese microstructure; functional cheese; green tea; polyphenol.

Figure 1

Total phenolic contents (TPC) of the control and full-fat cheeses enriched with different concentrations of free (+)-catechin over a 90-day ripening period reported in gallic acid equivalents (GA eq) per 100 g of cheese weight. Cont: control. Columns with different superscript letters differ significantly at p ≤ 0.05.

Figure 2

FRAP antioxidant activity of control and (+)-catechin-treated cheeses during 90 days of ripening, expressed as FeSO₄ equivalent (mmol·kg⁻¹ of fresh weight). Cont: control. Columns with different superscript letters differ significantly at p ≤ 0.05.

Figure 3

ORAC antioxidant activity of control cheese and cheeses containing different concentrations of free (+)-catechin during 90 days of ripening, expressed as Trolox equivalents per gram (Teq, µmol·g⁻¹) of fresh weight. Cont: control. Columns with different superscript letters differ significantly at p ≤ 0.05.

Figure 4

Retention coefficients of three different concentrations of free (+)-catechin in full-fat cheeses measured by HPLC. Columns with different superscript letters differ significantly at p ≤ 0.05.

Figure 5

Transmission electron micrographs (lower magnification) of mature full-fat cheese samples (a) no catechin (control cheese), (b) 250 ppm free (+)-catechin and (c) 500 ppm free (+)-catechin. The white areas represent fat globules, and the dark areas are protein (casein) matrix surrounding the fat globules. Scale bar: 5 µm.

Figure 6

Transmission electron micrographs (higher magnification) of mature full-fat cheese samples (a) no catechin (control cheese), (b) 250 ppm free (+)-catechin and (c) 500 ppm free (+)-catechin. The white areas represent fat globules, and the dark areas are protein (casein) matrix surrounding the fat globules. Scale bar: 500 nm.

Figure 7

Representative infrared reflection spectra of control and catechin-treated cheese samples. Cont: control full-fat cheese containing no catechin, 250 ppm: full-fat cheese containing 250 ppm of free (+)-catechin, 500 ppm: full-fat cheese containing 500 ppm of free (+)-catechin.